A cam system of this kind, for flat-bed knitting machines, of which the knitting cam is embodied with an integrated loop transferring cam for both carriage travel and loop transferring directions, and which is provided with a depressor apparatus, is known from German Offenlegungsschrift No. 33 15 283 (FIG. 9). In this known cam system, a great number of moving cam parts are provided, which despite the depressor apparatus must necessarily be indexed so as to enable selective operation of the needle cam unit, namely knitting, transfer, reception, tucking (that is, the position assumed between, successive knitting operations) and non-knitting. Mechanically and electrically, this is relatively complicated and expensive. Moreover, for the sake of symmetry, a lobe of protrusion for biasing or pre-tensioning the loops during transfer has been omitted in this cam system. In this known cam system the receiving needles are retracted in the usual manner, simultaneously with or even earlier than the transferring needles, which disadvantageously affects the loop transferring operation.